|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Vitreous State Laboratory, The Catholic University of America, 620 Michigan Ave., N.E. Washington D.C. 20064, USA
2 Department of Mineral Sciences, Smithsonian Institution, Washington, D.C. 20560-0119, USA
3 Surface and Microanalysis Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-0001, USA
* E-mail address of corresponding author: davidm{at}vsl.cua.edu
Lattice dynamic calculations for the sepiolite and palygorskite structures using polarized Raman and FTIR spectra provide a fundamental basis for interpreting spectral features by assigning vibrational modes. The Si–O stretch and O–Si–O bond bending force constants determined for palygorskite are similar to equivalent values calculated previously for other phyllosilicates. The Mg–O bond stretch values, on the other hand, are about half of those determined for the equivalent Al–O and Mg–O bond stretch environments in other phyllosilicates, suggesting that the bonding within the octahedral ribbons in palygorskite and sepiolite is weaker than that in the continuous octahedral sheets in micas. The weaker bonding allows more flexible octahedral environments in palygorskite and sepiolite, giving rise to higher probabilities for cation substitutions and vacancies relative to the micas. Above ~700 cm–1 in the IR and 750 cm–1 in the Raman spectra, the eigenmodes are dominated by atomic displacements within the silicate sheets. Below 700 cm–1 the eigenmodes become mixed with motions among the Mg octahedra and the silicate sheets; the eigenmodes assigned to the most prominent peaks in the Raman spectra (near 700 cm–1) belong to this group. As mode frequencies decrease, the corresponding eigenmodes evolve from more localized Mg-O stretch, O-Mg-O bend and O-Si-O bend motions to longer-range motions such as silicate sheet deformations caused by silicate tetrahedra rotation and silicate sheet shearing around the Mg-octahedral sheets.
Key Words: FTIR • Palygorskite • Raman • Sepiolite
This article has been cited by other articles:
|
|
 |
|
  M. Onal, H. Yilmaz, and Y. Sarikaya SOME PHYSICOCHEMICAL PROPERTIES OF THE WHITE SEPIOLITE KNOWN AS PIPESTONE FROM ESKISEHIR, TURKEY Clays and Clay Minerals, October 1, 2008; 56(5): 511 - 519. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 V. Gionis, G. H. Kacandes, I. D. Kastritis, and G. D. Chryssikos On the structure of palygorskite by mid- and near-infrared spectroscopy American Mineralogist, July 1, 2006; 91(7): 1125 - 1133. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. SUAREZ and E. G. ROMERO Macroscopic palygorskite from Lisbom Volcanic Complex European Journal of Mineralogy, February 1, 2006; 18(1): 119 - 126. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. Kuang, W. Kuang, G. A. Facey, and C. Detellier DEHYDRATION AND REHYDRATION OF PALYGORSKITE AND THE INFLUENCE OF WATER ON THE NANOPORES Clays and Clay Minerals, October 1, 2004; 52(5): 635 - 642. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. FRITSCH, E. GAILLOU, M. OSTROUMOV, B. RONDEAU, B. DEVOUARD, and A. BARREAU Relationship between nanostructure and optical absorption in fibrous pink opals from Mexico and Peru European Journal of Mineralogy, October 1, 2004; 16(5): 743 - 752. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Garcia-Romero, E. Garcia-Romero, M. S. Barrios, and M. A. Bustillo Revuelta CHARACTERISTICS OF A Mg-PALYGORSKITE IN MIOCENE ROCKS, MADRID BASIN (SPAIN) Clays and Clay Minerals, August 1, 2004; 52(4): 484 - 494. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
